A pair of researchers at the University of California, Santa Barbara has concluded that when it comes to sharing, there is little difference between human and non-human primates—all expect something in return. In their paper published in Proceedings of the Royal Society B, anthropologists Adrian Jaeggi and Michael Gurven describe their analysis of 32 separate studies on sharing, and found that all primates appear to have an ulterior motive when they share food with others.
The studies analyzed by the duo included field studies of monkeys, apes, and human societies that still relied on hunting or foraging for their survival. They were searching for an answer to the age-old question: do people (and/or other primates) always have an ulterior motive when sharing a resource with someone else? Put another way, is there really such a thing as pure altruism? Jaeggi and Gurven say no; their research indicates that when primates share, they always expect something back in return.
One area where the researchers found a difference between humans and other primates was in the type of reciprocity expected. According to the reviewed studies, apes and monkeys generally expect to get food in return at a later time for food shared, while humans are more likely to accept in-kind donations. This, the researchers say, is apparently due to the nature of the way food is obtained. For humans, food acquisition is generally balanced across a community which means there is equal risk among the population of coming up short at any given time. Sharing by others in the group helps fill the gaps. Thus, those that share can be confident that others will do the same for them should the need arise. But unlike other primates, humans are often willing to accept in-kind donations instead of food to make things even, which led to another observation. All of the groups studied appear to maintain forms of unofficial score-keeping. Monkeys, apes, and humans all keep a tally of who gave what to whom, and who still owes someone for what they received.
This new research may or may not apply to communities of primates, most particularly humans, where the food supply is essentially limitless. Thus for now, there is still no clear answer regarding true altruism as it applies to resources.